The ionic composition of the non-ideal plasma produced by a metallic sphere isothermally expanding into vacuum

A physical model of the non-ideal plasma of a vacuum arc cathode flare is presented. Expressions for the electronic transport coefficients valid for the condensed and plasma states are obtained and a method for the calculation of the equilibrium ionization state of the plasma is developed for a wide range of pressures and temperatures. To study the conditions under which the cathode plasma ionic composition forms, a modelling problem of a metallic sphere expanding into vacuum is solved. The non-equilibrium plasma ionic composition is found by solving the balance equations for particles, in which the reaction rates are calculated in a quasi-classical approximation by taking into account the possibility of the formation of frozen ionization states.